The demand for increased storage capacity in memory or rigid disks and the trend towards miniaturization of memory or rigid disks (due to the requirement for smaller hard drives in computer equipment) continues to emphasize the importance of the memory or rigid disk manufacturing process, including the planarization or polishing of such disks for ensuring maximal performance. While there exist several chemical-mechanical polishing (CMP) compositions and methods for use in conjunction with semiconductor device manufacture, few conventional CMP methods or commercially available CMP compositions are well-suited for the planarization or polishing of memory or rigid disks.
As the demand for increased storage capacity has increased, so has the need for improved processes for the polishing of such memory or rigid disks. The term “memory or rigid disk” refers to any magnetic disk, hard disk, rigid disk, or memory disk for retaining information in electromagnetic form. The memory or rigid disk typically has a surface that comprises nickel-phosphorus, but the memory or rigid disk surface can comprise any other suitable material. The planarity of the memory or rigid disks must be improved, as the distance between the recording head of a disk drive and the surface of the memory or rigid disk has decreased. Reduction of defectivity of the memory or rigid disk, that is, the reduction of surface roughness, is necessary to increase recording density. In order to increase recording density, recording density per unit area on the memory or rigid disk must also be increased.
During the polishing of a memory or rigid disk, typically the edges of the disk receive a higher pressure from the polishing tool than the remaining surface area of the disk. Typically, polishing is performed using a combination of an abrasive, a polishing pad, and a liquid carrier, in which the abrasive may be suspended in the liquid carrier, or may be affixed to the surface of the pad. As the polishing process mainly consists of mechanical abrasion of the disk by the abrasive and/or pad, in conjunction with the action of chemicals that may be present, and the rate of abrasion is at least in part a function of pressure applied, the edges of the disk experience a higher rate of abrasion than the rest of the disk. This leads to the formation of a curved, or rounded, contour at the edges of the disk, known in the art as rub-off or dub-off. Such rounded areas on a disk are unsuitable for recording. Thus, if the amount of rub-off can be reduced, the recording capacity for a disk can be increased.
Therefore, considerable effort has been expended in a search for improved processes for the uniform polishing of memory or rigid disks. For example, U.S. Pat. No. 6,488,729 discloses a polishing composition comprising a polishing material, a polishing accelerator, hydroxypropyl cellulose or hydroxyalkyl alkyl cellulose, and water. U.S. Pat. No. 6,645,051 discloses a polishing composition for a memory hard disk comprising a polyoxyethylene polyoxypropylene alkyl ether or a polyoxyethylene polyoxypropylene copolymer, an inorganic or organic acid, an abrasive, and water.
There remains a need, however, for other compositions and methods for planarizing or polishing memory or rigid disks at a high rate, while minimizing surface defectivity. The invention provides such a composition and method. These and other advantages of the invention, as well as additional inventive features, will be apparent from the description of the invention provided herein.